1. Field of the Invention
The present invention relates to a semiconductor wafer evaluation method, a semiconductor wafer evaluation device, and a probe for a semiconductor evaluation device.
Priority is claimed on Japanese Patent Application, No. 2012-154703, filed on Jul. 10, 2012, the contents of which are incorporated herein by reference.
2. Description of Related Art
As a method of measuring characteristics of carrier density of a semiconductor wafer and the like such as an epitaxial wafer that forms an epitaxial layer on a wafer of a silicon wafer, SiC wafer and so forth, a mercury probe method using mercury for an electrode is known. This method is called “Hg-CV method” in the present invention.
Hg-CV method is a type of capacity-voltage methods. The method, first, forms a Schottky junction by contacting a tip end of the mercury probe on a surface of the semiconductor wafer. In a case where an object to be measured is an epitaxial wafer, the “surface of the semiconductor wafer” refers to the surface of the epitaxial layer. In addition, the mercury probe is obtained by injecting mercury in a capillary (holder for holding the mercury) tube made of glass or the like. Next, capacitance (C)-reverse voltage (V) characteristics are measured across the Schottky junction formed on the surface of the semiconductor wafer, and donor density and the like are calculated from measurement result of the C-V characteristics. In a case where an oxide film is formed on the surface of the semiconductor wafer (considered as a structure of metal-oxide film-semiconductor (MOS structure)), MOS-CV measurement is performed. The C-V characteristics can also be measured in the MOS structure, a merit of the Hg-CV method is that a pre-treatment (formation of an oxide film, formation of an electrode and the like) is not necessary. In a case where the Schottky junction with the Hg is not formed, the MOS structure is made. In other words, there is a case where the C-V characteristics is measured by forming the oxide film on the surface of the semiconductor wafer using the Hg electrode.
As a device using the Hg-CV method, a semiconductor evaluation device is known which performs evaluation of electrical characteristics by bringing the mercury probe supported in a state of being freely movable in a direction perpendicular to the surface of the semiconductor wafer into contact with the surface of the semiconductor wafer (for example, refer to Japanese Unexamined Patent Application, First Publication No. 2010-153611). In addition, a measurement device of the semiconductor wafer is disclosed in which the mercury probe is held by a probe arm and the probe arm having mapping capability is horizontally-movable and rotationally-movable (for example, refer to Japanese Unexamined Patent Application, First Publication No. H06-140478). Further, an low-melting-point pad for an electrical connector is disclosed in which an n-type or p-type conductivity type semiconductor and a contact pad are sequentially laminated on a low-melting-point adhesive layer and a wire is connected to the contact pad thereof (for example, refer to U.S. Pat. No. 6,144,039).
FIG. 7 illustrates a configuration of the semiconductor wafer evaluation device in the related art. A semiconductor wafer evaluation device 200 includes mercury 52, a capillary 53 accommodating the mercury 52, a supply and exhaust pipe 54 that supplies and exhausts the interior of the capillary 53, a wire 55 that is electrically connected to the mercury 52, and an electrical characteristic measurement unit (not shown) that is electrically connected to the wire 55 and a semiconductor wafer 51 to be measured, and measures the electrical characteristics of the semiconductor wafer 51 by applying an electrical stimulation to the semiconductor wafer 51.
When measuring the electrical characteristics of carrier density of the semiconductor wafer using the semiconductor wafer evaluation device 200, as illustrated in FIG. 8, first, the interior of the capillary 53 is exhausted through the supply and exhaust pipe 54 and then the capillary 53 is lifted in a state where the mercury 52 is held in the air of the capillary 53. Next, as illustrated in FIG. 9, the capillary 53 is lowered, air is supplied to the interior of the capillary 53, and the mercury 52 is lowered so that a bottom end of the mercury 52 is in contact with the semiconductor wafer 51. Then, an electrical signal is transmitted via the wire 55 connected to the mercury 52, and the response is retrieved from the wire 55. When parameters and the response of the electrical signal are retrieved, the electrical characteristics of the semiconductor wafer 51 are obtained.
In the above-described Hg-CV method, an area of the mercury electrode brought in to contact with the surface of the semiconductor wafer (mercury electrode area) has an effect on the calculation of the electrical characteristics. For this reason, in the Hg-CV method, it is important to accurately obtain an area of the mercury electrode. In a case of using the mercury probe in which the mercury is injected into the interior of a tube of the capillary (holder for holding the mercury) made of glass or the like, the area of the mercury electrode is a cross-sectional area of the capillary.